1. Field of the Invention
The present invention relates to a rotary tool.
2. Related Art
Generally, a rotary tool such as an impact wrench is rotated only while a trigger is pulled, and is stopped rotating when the trigger is released. In a case a bolt is tightened by the rotary tool, there is a problem that the bolt is excessively tightened and thus elongated when the trigger is pulled for a long time. Further, there is also a problem that electricity is wasted when the trigger is pulled unnecessarily and thus an amount of available operations per a single electric charge is decreased.
In order to avoid the above problems, there is a rotary tool whose rotational movement is automatically stopped in a predetermined condition. For example, JP-A-2006-062065 discloses an electric rotary tool configured as follows. That is, a load current value or a voltage value for an electric motor is preset, which corresponds to an optimal screw tightening torque value depending on a type of a screw, a signal to determine the type of screw is generated when taking out a selected screw from a screw supply part, the load current value or voltage value of the electric motor corresponding to the optimal screw tightening torque value for the selected screw is automatically selected and set, and a drive stop control is carried out when the screw tightening with the optimal screw tightening torque by the electric motor is completed.
However, the rotary tool disclosed has a problem that variation occurs in the load current value or voltage value depending on each operator and thus the automatic stop does not necessarily obtain the intended result. Further, there is also a problem that it is difficult for the operator to adjust conditions of the automatic stop depending on a situation in a site and therefore usability is poor.